Certain antioxidants are known to inhibit the production of cancers from polycyclic hydrocarbons in test animals. The mechanism of this inhibition is not fully understood. In this study it is proposed to investigate the effects of various antioxidants and combinations of antioxidants on the in vitro metabolism of benzo(a)pyrene by rat liver microsomes. The methods to be used in this study will be electron paramagnetic resonance spectroscopy which will be used to monitor the production of 6-hydroxybenzo(a)pyrene via the formation of the 6-oxygenzo(a)pyrene free radical, high pressure liquid chromatography which wil be used to monitor the production of stable benzo(a)pyrene metabolites, and the Ames test which will be used to study the effect of antioxidants on the production of mutagenic metabolites. Additional experiments will be concerned with the effect of alkyl substituents on the oxidative and carcinogenic properties of benzo(a)pyrene.